Ammonium perchlorate-ammonium nitrate explosive composition containing excess chloride ion

ABSTRACT

AN AMMONIUM PERCHLORATE EXPLOSIVE COMPOSITION COMPRISING AMMONIUM PERCHLORATE, AT LEAST 5% BY WEIGHT OF AMMONIUM NITRATE, AT LEAST 0.003% BY WEIGHT OF A METAL AND AT LEAST ONE CHLORIDE ANION PER METAL ATOM IN EXCESS OF THE RATIO OF CHLORIDE ANION TO METAL ATOM THAT WOULD BE OBTAINED BY ADDING THE METAL AS ITS CHLORIDE SALT.

Jan; 5, 1971 A. G. KEENAN ETAL AMMONIUM PERCHLORATE-AMMONIUM NITRATEEXPLOSIVE COMPOSITION CONTAINING EXCESS CHLORIDE ION Filed July 15, 1968A nUov UEDEQ Qua EMC.

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ARTHUR GKEENAN If IVENTORS TIME (MIN) AT TO RN EYS United States PatentAMMONIUM PERCHLORATE-AMMONIUM NI- TRATE EXPLOSIVE COMPOSITION CON-TAINING EXCESS CHLORIDE ION Arthur G. Keenan and Robert F. Siegmund,Miami, Fla., assignors to Research Corporation, New York, N.Y., anonprofit corporation of New York Filed July 15, 1968, Ser. No. 744,989Int. Cl. C06b N04 US. Cl. 14941 4 Claims ABSTRACT OF THE DISCLOSURE Anammonium perchlorate explosive composition comprising ammoniumperchlorate, at least 5% by weight of ammonium nitrate, at least 0.003%by weight of a metal and at least one chloride anion per metal atom inexcess of the ratio of chloride anion to metal atom that would beobtained by adding the metal as its chloride salt.

This invention relates to ammonium perchlorate gas producing orexplosive compositions, and more particularly to ammonium perchloratecompositions having an improved decomposition rate.

Ammonium perchlorate is used as an oxidizer in propellants and otherexplosive compositions. Various combustion catalysts have heretoforebeen added singly or in combination to ammonium perchlorate in order toimprove its decomposition characteristics. We have now discovered thatthe decomposition of ammonium perchlorate is greatly improved by addingammonium nitrate, a metal, and an excess of chloride anions with respectto the amount of metal added.

More specifically, the present invention is an ammonium perchlorateexplosive composition comprising ammonium perchlorate, at least 5% byweight of ammonium nitrate, at least 0.003% by weight of a metal and atleast one chloride anion per metal atom in excess of the ratio ofchloride anion to metal atom that would be obtained by adding the metalas its chloride salt.

The composition of the present invention is made by incorporatingammonium nitrate, the metal or metal-containing additive and thechloride anion-containing additive into ammonium perchlorate, generallyby milling or dry mixing the ingredients. The resultant mixture may beshaped or pressed or otherwise prilled to the form of compacted grains.

The metal may be added as the free metal, or, preferably, in combinedform. It is generally most convenient to use a readily available saltcontaining the metal as a cation or as part of the anion. A list of suchsuitable salts would include nitrates, carbonates, sulfates, chromates,dichromates and the like. The metal may also be present in both thecation and anion as, for example, copper chromite.

The decomposition characteristics of ammonium perchlorate are improvedby the incorporation of at least 0.003% of a metal provided ammoniumnitrate and excess chloride anion are also present as more fullydiscussed below. The beneficial effect of metal addition increases withincreasing the metal content of the composition until either the diluenteffect and/ or the decreasing solubility of the metal andchloride-containing additives tend to exhibit a contrary effect. Thereis no theoretical upper limit for the amount of additives which may beemployed since these adverse factors vary widely with the particularadditives employed. Satisfactory explosive compositions containing ashigh as 5% by weight of metal and excess chloride anion have beenprepared and tested. It is doubtful that compositions in which theamount of metal and chloride additive exceeds 5% by weight of thecomposition would be useful in practice except possibly in Very specialsituations.

The rate of improvement obtained using metal-chloride combustioncatalysts in an ammonium perchlorate composition according to thepresent invention with various metals was determined by thermographicanalysis. In order of decreasing effectiveness, the metals are:

Chromium Titanium Copper Lead Silver Manganese Nickel Mercury IronBismuth Gold Platinum Palladium Zinc Cobalt Cadmium Cerium AluminumZirconium Metals listed in the first column are particularly effective.Metals having a standard oxidation potential above 2.0 volts, i.e., thealkali metals such as lithium, potassium, sodium, et cetera, are muchless eifective.

The composition according to the present invention should also containat least one and preferably ten chloride anions per metal atom in excessof the ratio of chloride anion to metal atom that would be obtained byadding the metal as its chloride salt. The decomposition characteristicsof the composition improve, but to a lesser extent, as 30-40 chlorideanions per metal atom are added. Relatively little further improvementis noted as additional chloride is provided. The particular saltemployed as the chloride carrier is not determinative; the chlorides ofsodium, potassium and ammonium are preferred because of their readyavailability at low cost.

The beneficial effects of metal and excess chloride anion addition onthe decomposition rate of ammonium perchlorate are not obtained unlessammonium nitrate is added as well. Generally speaking, compositionscontaining at least about 5% and preferably about 5-15 by weight ofammonium nitrate give the best results. The amounts of the variousadditives to be provided are interrelated since the minimum amount of agiven additive required depends on how much of the others is present.For example, the minimal concentrations of metal and chloride may bedecreased somewhat by increasing the amount of ammonium nitrate added;the minimal concentration of the metal may be decreased by increasingthe amount of chloride added. It is apparent that compositionscontaining minimal amounts of the metal would be the most desirable inpractice. One of the advantages of the present composition is that theyrequire less of the metal-containing additive than is generally employedin ammonium perchlorate explosive or propellant compositions.

The shortening of the induction period and the improved decomposition ofammonium perchlorate obtained according to the present invention weremeasured by thermographic analysis. Compositions containing ammoniumperchlorate, ammonium nitrate, and a metal salt, with or without addedsodium chloride, were prepared and weighed into glass reactor tubes andplaced in a furnace programmed to maintain a constant temperature of 295C. The more active samples deflagrated on reaching about 250 C.; theothers decomposed just prior to reaching furnace temperature.

The curves shown in FIGS. 1 and 2 of the drawing are graphs oftemperature against time as measured by a thermocouple set in the testcompositions. Curve A is the thermograph obtained on a test compositioncontaining parts by weight of ammonium perchlorate, 10 parts by weightof ammonium nitrate and 0.0135% by weight of potassium dichromate. Onlya partial decomposition and moderate temperature rise occurred leaving aresidue of about 70% undecomposed material. Curve B shows the results ona similar composition except that 0.16% by weight of sodium chloride wasadded. Complete decomposition occurred sending the temperature otfscale. The test composition of curve C contained 85% ammoniumperchlorate, 15% ammonium nitrate and 0.03% by weight of potassiumdichromate. Even though the amount of nitrate and dichromate was greatlyincreased over that present in the composition of curve A, nosignificant improvement in decomposition was obtained. The testcomposition of curve D contained 92 parts by weight of perchlorate, 8parts by weight of ammonium nitrate, 0.015% by weight of dichromate and0.23% by weight of sodium chloride. Even though the amounts of nitrateand dichromate were less than that of the composition of curve C, theaddition of chloride gave an extremely strong decomposition. Similarresults were obtained with compositions containing 942 parts We claim:

1. An ammonium perchlorate explosive composition comprising ammoniumperchlorate, at least 5% by weight of ammonium nitrate, at least 0.003%by weight of a metal and at least one chloride anion per metal atom inexcess of the ratio of chloride anion to metal atom that would beobtained by adding the metal as its chloride salt.

2. A composition according to claim 1 wherein the metal is chromium,copper, silver, nickel, iron, gold, palladium, cobalt or cerium.

3. A composition according to claim 1 containing 5-15 by weight ofammonium nitrate and at least ten chloride anions per metal atom.

4. An ammonium perchlorate explosive composition comprising 90 parts byweight of ammonium perchlorate and 10 parts by weight of ammoniumnitrate, 0.0135 by weight of potassium dichromate and 0.16% by weight ofsodium chloride.

References Cited UNITED STATES PATENTS 3,336,171 8/1967 Keenan et al.149-43 CARL D. QUARFORTH, Primary Examiner S. J. LECHERT, JR., AssistantExaminer US. Cl. X.R. 14942, 43, 46, 76

